Working with the File and Operating System

Abstract

These days it’s rare to write an application that is entirely self-sufficient—that is, one that does not rely on at least some level of interaction with external resources, such as the underlying file and operating system or even other programming languages. The reason for this is simple: as languages, file systems, and operating systems mature, the opportunities for creating much more efficient, scalable, and timely applications increases greatly as a result of the developer’s ability to integrate the most powerful features of each technology into a singular product. Of course, the trick is to choose a language that offers a convenient and efficient means for doing so. Fortunately, PHP satisfies both conditions quite nicely, offering the programmer a wonderful array of tools not only for handling file system input and output, but also for executing programs at the shell level. This chapter serves as an introduction to these features, including the following topics:

• Files and directories: You’ll learn how to perform file system forensics, revealing details such as file and directory size and location, modification and access times, and more.

• File I/O: You’ll learn how to interact with data files, which will let you perform a variety of practical tasks, including creating, deleting, reading, and writing files.

• Directory contents: You’ll learn how to easily retrieve directory contents.

• Shell commands: You can take advantage of operating system and other language-level functionality from within a PHP application through a number of built-in functions and mechanisms.

• Sanitizing input: This section demonstrates PHP’s input sanitization capabilities, showing you how to prevent users from passing data that could potentially cause harm to your data and operating system.